Remote front-end for a multi-antenna station

ABSTRACT

A multi-antenna station has multiple remote front-ends coupled to multiple antennas. Each remote front-end includes a power amplifier (PA), a low noise amplifier (LNA), and first and second coupling units. On the transmit path, a first RF signal is received via a first port, routed by the first coupling unit to the power amplifier, amplified to obtain the desired output power level, and routed by the second coupling unit to a second port for transmission via the antenna. On the receive path, a second RF signal is received via the second port, routed by the second coupling unit to the LNA, amplified to obtain a higher signal level, and routed by the first coupling unit to the first port for transmission to the transceiver.

CLAIM OF PRIORITY UNDER 35 U.S.C. §119

The present Application for Patent claims priority to ProvisionalApplication Ser. No. 60/615,891, entitled “Remote Front-End for aMulti-Antenna Station,” filed Oct. 4, 2004, assigned to the assigneehereof, and expressly incorporated herein by reference.

BACKGROUND

1. Field

The present invention relates generally to electronics, and morespecifically to a wireless multi-antenna station.

2. Background

A multiple-input multiple-output (MIMO) communication system employsmultiple (T) transmit antennas at a transmitting station and multiple(R) receive antennas at a receiving station for data transmission. AMIMO channel formed by the T transmit antennas and R receive antennasmay be decomposed into S spatial channels, where S≦min{T, R}. The Sspatial channels may be used to transmit data in parallel to achievehigher throughput and/or redundantly to achieve greater reliability.

A multi-antenna station is equipped with multiple antennas that may beused for data transmission and reception. Each antenna is typicallyassociated with a transceiver that includes (1) transmit circuitry usedto process a baseband output signal and generate a radio frequency (RF)output signal suitable for transmission via the antenna and (2) receivecircuitry used to process an RF input signal received via the antennaand generate a baseband input signal. The multi-antenna station also hasdigital circuitry for processing data for transmission and reception.

The antennas of the multi-antenna station may not be located near thetransceivers for various reasons. For example, it may be desirable toplace the antennas at different locations and/or with sufficientseparation in order to (1) decorrelate the spatial channels as much aspossible and (2) achieve good reception of RF input signals andtransmission of RF output signals. As another example, the multi-antennastation may be designed such that it is not possible to locate theantennas near their associated transceivers. In any case, if theantennas are not located near the transceivers, then relatively long RFcables or transmission lines are needed to connect the antennas to thetransceivers. A fair amount of signal loss may result from the longconnection between the antennas and the transceivers. This signal lossincreases the receiver noise figure on the receive path and lowers thetransmit power level on the transmit path. These effects make the systemless power efficient and degrade performance.

There is therefore a need in the art for techniques to connect theantennas to the transceivers.

SUMMARY

Techniques for connecting multiple antennas to multiple transceivers ina multi-antenna station are described herein. According to an embodimentof the invention, a station equipped with multiple antennas is describedwhich includes multiple transceivers and multiple remote front-ends.Each transceiver performs signal conditioning for RF signals transmittedand received via an associated antenna. Each remote front-end couples toan associated transceiver and an associated antenna, amplifies a firstRF signal received from the associated transceiver to generate a firstamplified RF signal for transmission from the associated antenna, andfurther amplifies a second RF signal received from the associatedantenna to generate a second amplified RF signal for transmission to theassociated transceiver.

According to another embodiment, a station equipped with multipleantennas is described which includes means for performing signalconditioning for RF signals transmitted and received via the antennas,means for power amplifying RF modulated signals received from the meansfor performing signal conditioning to generate amplified RF modulatedsignals for transmission from the antennas, and means for low noiseamplifying RF input signals received from the antennas to generateamplified RF input signals for transmission to the means for performingsignal conditioning. The means for power amplifying and the means forlow noise amplifying are separate from the means for performing signalconditioning.

According to yet another embodiment, an apparatus suitable for use witha station equipped with multiple antennas is described which includesfirst and second amplifiers and first and second coupling units. Thefirst amplifier receives and amplifies a first radio frequency (RF)signal and provides a first amplified RF signal. The second amplifierreceives and amplifies a second RF signal and provides a secondamplified RF signal. The first coupling unit couples the first RF signalfrom a first port to the first amplifier and couples the secondamplified RF signal from the second amplifier to the first port. Thesecond coupling unit couples the first amplified RF signal from thefirst amplifier to a second port and couples the second RF signal fromthe second port to the second amplifier.

According to yet another embodiment, an apparatus suitable for use witha station equipped with multiple antennas is described which includesmeans for amplifying a first RF signal to generate a first amplified RFsignal, means for amplifying a second RF signal to generate a secondamplified RF signal, means for coupling the first RF signal from a firstport to the means for amplifying the first RF signal, means for couplingthe first amplified RF signal to a second port, means for coupling thesecond RF signal from the second port to the means for amplifying thesecond RF signal, and means for coupling the second amplified RF signalto the, first port.

According to yet another embodiment, a transceiver module for use in astation equipped with multiple antennas is described which includesfirst and second transceivers, an oscillator, and a driver. Eachtransceiver performs signal conditioning for RF signals transmitted andreceived via an associated set of at least one antenna.

The oscillator generates local oscillator (LO) signals used by the firstand second transceivers for frequency conversion between baseband andRF. The driver receives the LO signals from the oscillator and drivesthe LO signals from the transceiver module.

According to yet another embodiment, a transceiver module for use in astation equipped with multiple antennas is described which includesmeans for performing signal conditioning for RF signals transmitted andreceived via at least two antennas, means for generating LO signals usedfor frequency conversion between baseband and RF, and means for drivingthe LO signals from the transceiver module.

Various aspects and embodiments of the invention are described infurther detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a multi-antenna station.

FIG. 2A shows a remote front-end for a time division duplexed (TDD)system.

FIG. 2B shows a remote front-end for a frequency division duplexed (FDD)system.

FIGS. 3, 4 and 5 show three embodiments for coupling the remotefront-end to a transceiver.

FIG. 6 shows connection of the remote front-end to a cable and anantenna.

FIG. 7 shows a block diagram of a MIMO unit within the multi-antennastation.

FIG. 8 shows a block diagram of 2×2 transceiver modules.

FIG. 9 shows a block diagram of the transceivers within the transceivermodules.

DETAILED DESCRIPTION

The word “exemplary” is used herein to mean “serving as an example,instance, or illustration.” Any embodiment described herein as“exemplary” is not necessarily to be construed as preferred oradvantageous over other embodiments.

FIG. 1 shows a block diagram of a multi-antenna station 100, which isequipped with N antennas 150 a through 150 n, where N≧2. Multi-antennastation 100 may be a wireless communication device, a user terminal, atelevision, a digital video disc (DVD) player, an audio/video (AV)equipment, a consumer electronics unit, or some other device orapparatus. In the following description, a reference numeral with acharacter (e.g., “150 a”) denotes a specific instance or embodiment ofan element, block, or unit. A reference numeral without a character(e.g., “150”) can denote all of the elements with that reference numeral(e.g., antennas 150 a through 150 n) or any one of the elements withthat reference numeral, depending on the context in which the referencenumeral is used.

Multi-antenna station 100 includes a MIMO unit 110 and N remotefront-ends (RFEs) 140 a through 140 n for N antennas 150 a through 150n, respectively. MIMO unit 110 includes a MIMO processor 120 and Ntransceivers 130. MIMO processor 120 performs digital processing fordata transmission and reception. N transceivers 130 perform signalconditioning (e.g., amplification, filtering, frequencyupconversion/downconversion, and so on) on the RF signals for the Nantennas 150. N transceivers 130 couple to N remote front-ends 140 athrough 140 n via cables 142 a through 142 n, respectively. Remotefront-ends 140 a through 140 n further couple to N antennas 150 athrough 150 n, respectively, via cables 144 a through 144 n,respectively. Antennas 150 may be located either close to or somedistance away from MIMO unit 110, depending on the design ofmulti-antenna station 100.

Remote front-ends 140 condition (e.g., amplify and filter) RF modulatedsignals received from transceivers 130 and generate RF output signalsfor transmission from antennas 150. Remote front-ends 140 also conditionRF input signals received from antennas 150 and generate conditioned RFinput signals for transceivers 130. Remote front-ends 140 are located asclose as possible to antennas 150 to reduce the signal loss in cables144 between remote front-ends 140 and antennas 150.

Remote front-ends 140 may be optional, and may or may not be installeddepending on various factors such as the supported applications, thedesired performance, cost, and so on. Remote front-ends 140 may beinstalled to reduce signal loss between antennas 150 and transceivers130, which may be desirable or necessary if the distance between theantennas and the transceivers is relatively long and the supportedapplications require high data rates. Remote front-ends 140 may beomitted for lower rate applications and/or if the distance betweenantennas 150 and transceivers 130 is relatively short. If remotefront-ends 140 are omitted, then antennas 150 couple directly totransceivers 130 via cables 142.

FIG. 2A shows a block diagram of an embodiment of a remote front-end 140v, which may be used for each of remote front-ends 140 a through 140 nin FIG. 1. Remote front-end 140 v may be used for a TDD communicationsystem that transmits data on the downlink and uplink on the samefrequency band at different times. For example, data may be sent on onelink (e.g., downlink) in a first portion or phase of each TDD frame, anddata may be sent on the other link (e.g., uplink) in a second portion ofeach TDD frame. The first and second portions may be static or maychange from TDD frame to TDD frame.

For the embodiment shown in FIG. 2A, remote front-end 140 v includesswitches 210 and 240, a power amplifier (PA) 220, a low noise amplifier(LNA) 230, and a bandpass filter 250. Switch 210 couples to a first portof remote front-end 140 v, which further couples to a transceiver 130.Filter 250 couples to a second port of remote front-end 140 v, whichfurther couples to an antenna 150. Switches 210 and 240 receive atransmit/receive (T/R) control signal that indicates whether RF signalsare being transmitted or received by multi-antenna station 100. Eachswitch couples its input to a “T” output during the transmit portion andto an “R” output during the receive portion.

The transmit and receive portions are indicated by the T/R controlsignal. Switch 210 allows remote front-end 140 v to receive an RFE inputsignal from transceiver 130 and send an RFE output signal to thetransceiver via a single port. This simplifies the connection betweenremote front-end 140 v and transceiver 130.

For the transmit path, which is active during the transmit portion,switch 210 receives an RF modulated signal (which is the RFE inputsignal) from transceiver 130 via the first port and routes this RFEinput signal to power amplifier 220. Power amplifier 220 amplifies theRFE input signal with a fixed or variable gain and provides the desireoutput signal level. Switch 240 receives the amplified RFE input signalfrom power amplifier 220 and routes this signal to filter 250. Filter250 filters the amplified RFE input signal to remove out-of-band noiseand undesired signal components and provides an RF output signal via thesecond port to antenna 150.

For the receive path, which is active during the receive portion, filter250 receives an RF input signal from antenna 150 via the second port,filters this RF input signal, and provides a filtered RF input signal toswitch 240. Switch 240 routes the filtered RF input signal to LNA 230,which amplifies the signal. LNA 230 may also have a fixed or variablegain and is designed to provide the desire performance (e.g., to havethe desired noise figure). Switch 210 receives the amplified RF inputsignal (which is the RFE output signal) from LNA 230 and provides theRFE output signal via the first port to transceiver 130.

Remote front-end 140 v may be used to provide low loss for the RFsignals sent between the remote front-end and transceiver 130. Remotefront-end 140 v may also be used to provide the desired output powerlevel for the RF output signal transmitted from antenna 150. Forexample, transceiver 130 may be implemented on an RFIC and may becapable of providing low or medium output power level for the RFmodulated signal sent to remote front-end 140 v. Power amplifier 220within remote front-end 140 v may then provide amplification and highoutput power level for the RF output signal.

Power amplifier 220 and/or LNA 230 may be powered down whenever possibleto reduce power consumption. For example, power amplifier 220 (andpossibly LNA 230) may be powered down when multi-antenna station 100 isidle. To further reduce power consumption, power amplifier 220 may bepowered down during the receive portion based on the T/R control signal,and LNA 230 may be powered down during the transmit portion based on theT/R control signal, as indicated by the dashed line in FIG. 2A.

FIG. 2B shows an embodiment of a remote front-end 140 w that may be usedfor an FDD system. An FDD communication system can simultaneouslytransmit data on the downlink and uplink at the same time on differentfrequency bands. For the embodiment shown in FIG. 2B, remote front-end140 w includes duplexers 212 and 242, power amplifier 220, and LNA 230.For the transmit path, duplexer 212 filters the RFE input signalreceived via the first port and routes the filtered RFE input signal topower amplifier 220. Duplexer 242 filters the output signal from poweramplifier 220 and provides the filtered signal as the RF output signalto the second port. For the receive path, duplexer 242 filters the RFinput signal received via the second port and routes this signal to LNA230. Duplexer 212 filters the output signal from LNA 230 and providesthis signal as the RFE output signal to the first port. The T/R controlsignal is not needed for remote front-end 140 w.

FIGS. 2A and 2B show specific designs for remote front-ends 140 v and140 w, respectively. In general, the transmit and receive paths may eachinclude one or more stages of amplifier, filter, and so on. The transmitand receive paths may also include fewer, different, and/or additionalcircuit blocks not shown in FIGS. 2A and 2B. For example, switch 210 inFIG. 2A may be omitted, and the RFE input and output signals may be sentvia separate cables.

For the embodiment shown in FIG. 2A, remote front-end 140 v receives (1)the T/R control signal that toggles switches 210 and 240 between the “T”and “R” output ports and (2) a DC supply for the active circuits, e.g.,power amplifier 220 and LNA 230. The RF signals, T/R control signal, andDC supply may be provided to remote front-end 140 v in various manners,as described below.

FIG. 3 shows a first embodiment for coupling a remote front-end 140 x toa transceiver 130 x via a cable 142 x. Remote front-end 140 x includesall of the circuit blocks in remote front-end 140 v, which is describedabove in FIG. 2A. Remote front-end 140 x further includes a capacitor202, an inductor 204, and a power control unit 206. Capacitor 202couples between the first port of remote front-end 140 x and the inputof switch 210. Capacitor 202 performs AC coupling of the RFEinput/output signals and also performs DC blocking of the DC supplyvoltage. Inductor 204, which is often called an RF choke, couplesbetween the first port of remote front-end 140 x and power control unit206. Inductor 204 routes the DC supply voltage received via a coaxialcable 310 to power control unit 206 and further performs RF blocking.Power control unit 206 receives the DC supply voltage via inductor 204and provides the supply voltage for power amplifier 220, LNA 230, andother active circuit blocks (if any) within remote front-end 140 x.

At transceiver 130 x, an AC coupling/DC blocking capacitor 302 couplesthe RF signals between transceiver 130 x and coaxial cable 310. Aninductor 304 couples the DC supply voltage from a power source 306 tocoaxial cable 310. Capacitor 302 and inductor 304 at transceiver 130 xperform the same function as capacitor 202 and inductor 204,respectively, at remote front-end 140 x.

For the embodiment shown in FIG. 3, cable 142 x includes coaxial cable310 and a messenger cable 320. Coaxial cable 310 has a center conductor312 and an outer shield 314. Center conductor 312 carries RF signals aswell as the DC supply voltage between transceiver 130 x and remotefront-end 140 x. Outer shield 314 is electrically grounded at bothtransceiver 130 x and remote front-end 140 x. Coaxial cable 310 isdesigned to have the proper impedance (e.g., 50 Ω or 75 Ω) at theoperating frequency.

Messenger cable 320 has a center conductor 322 that carries the T/Rcontrol signal from MIMO processor 120 to remote front-end 140 x.Messenger cable 320 may share/utilize outer shield 314 of coaxial cable310 (as shown in FIG. 3) or may be provided with its own shield (notshown in FIG. 3). Messenger cable 320 is designed to provide goodperformance for the T/R control signal, e.g., good waveform fidelity forthe leading and trailing transitions in the T/R control signal. Coaxialcable 310 and messenger cable 320 may be bundled together for easyhandling. For example, both cables 310 and 320 may be coated with anouter insulation material (e.g., plastic). In this case, only onebundled cable connects remote front-end 140 x to transceiver 130 x andcarries all of the required signals and power, e.g., the RF signals, T/Rcontrol signal, and DC power.

FIG. 4 shows a second embodiment for coupling remote front-end 140 x totransceiver 130 x via a cable 142 y. For this embodiment, cable 142 yincludes a coaxial cable 410 and a twisted wire 420. Coaxial cable 410has (1) a center conductor 412 that carries the RF signals and DC supplyand (2) an outer shield 414 that is electrically grounded at bothtransceiver 130 x and remote front-end 140 x. Twisted wire 420 has afirst conductor 422 that carries the T/R control signal and a secondconductor 424 that is electrically grounded at both transceiver 130 xand remote front-end 140 x. Twisted wire 420 provides good performancefor the T/R control signal. Coaxial cable 410 may be any coaxial cablethat is commercially available, and twisted wire 420 may also be anycommercially available twisted wire. Coaxial cable 410 and twisted wire420 may be bundled together for easy handling. For example, coaxialcable 410 and twisted wire 420 may be coated with an outer insulationmaterial.

FIG. 5 shows a third embodiment for coupling a remote front-end 140 y toa transceiver 130 y via a cable 142 z. For this embodiment, cable 142 zincludes coaxial cable 410 and a twisted wire 520. Twisted wire 520 hasa first conductor 522 that carries the T/R control signal, a secondconductor 524 that carries the DC supply, and a third conductor 526 thatis grounded at both transceiver 130 y and remote front-end 140 y.Twisted wire 520 provides good performance for the T/R control signaland may be any commercially available twisted wire with three or moreconductors. Coaxial cable 410 and twisted wire 520 may be bundledtogether for easy handling. For the embodiment shown in FIG. 5, ACcoupling/DC blocking capacitors and RF choke inductors are not needed attransceiver 130 y and remote front-end 140 y because the DC supply isprovided via a dedicated wire instead of the center conductor of coaxialcable 410.

FIGS. 3 through 5 show three exemplary embodiments for sending signalsand DC power to a remote front-end. Signals and DC power may also besent in other manners. For example, a single coaxial cable may be usedto send the RF signals, T/R control signal, and DC supply. The T/Rcontrol signal may be conveyed by a change in the DC supply voltage,e.g., a Vhigh voltage for logic high on the T/R control signal and aVlow voltage for logic low on the T/R control signal. The T/R controlsignal may also be conveyed by pulses sent to indicate the start of thetransmit and receive portions. For example, a pulse of a first polarityand/or a first width may be sent at the start of the transmit portion,and a pulse of a second polarity and/or a second width may be sent atthe start of the receive portion. In general, each signal may be sentvia a wire, a cable, or some other medium capable of propagating thatsignal with a tolerable amount of loss.

The DC supply may be shut off if the remote front-ends are notinstalled. A sensing circuit within power source 306 in MIMO unit 110can detect whether the remote front-ends are installed. This detectionmay be achieved in various manners. For example, the amount of currentbeing consumed may be sensed, and no current consumption would indicatethat the remote front-ends are not installed. As another example, theimpedance of the wire carrying the DC supply may be sensed, and high oropen impedance would indicate that the remote front-ends are notinstalled. If the remote front-ends are not installed, then power source306 can shut off the DC supply.

FIG. 6 shows a diagram of an embodiment for connecting remote front-end140 x to cable 142 x and antenna 150 x. Remote front-end 140 x has afemale connector 620 for the first port and a male connector 630 for thesecond port. Cable 142 x has a male connector 610 that couples to femaleconnector 620 of remote front-end 140 x. Male connector 630 of remotefront-end 140 x couples to a female connector 640 for antenna 150 x.

For the embodiment shown in FIG. 6, remote front-end 140 x is coupled asclose as possible to antenna 150 x to reduce loss for the RFinput/output signals. Connector 640 may represent the bulk of cable 144x between remote front-end 140 x and antenna 150 x. The use of differentconnectors 620 and 630 for the first and second ports of remotefront-end 140 x prevents backward installation of remote front-end 140 xsince (1) the first port can couple to cable 142 x only via connector620 and (2) the second port can couple to antenna 150 x only viaconnector 630.

The use of complementary types of connectors (e.g., female connector 620and male connector 630) for the first and second ports of remotefront-end 140 x also allows for optional installation of remotefront-end 140 x. For example, remote front-end 140 x may be installed iflower loss is desired for applications requiring high data rates. Remotefront-end 140 x may be omitted for applications that can tolerate moreloss. In this case, cable 142 x would couple directly to antenna 150 xvia connectors 610 and 640.

FIG. 6 shows a specific embodiment for connecting remote front-end 140 xto cable 142 x and antenna 150 x. Other types of connectors may also beused for a remote front-end to achieve the desired connection, preventbackward installation of the remote front-end, and allow for optionalinstallation of the remote front-end.

FIG. 7 shows a block diagram of a MIMO unit 110 z, which is oneembodiment of MIMO unit 110 in FIG. 1. MIMO unit 110 z supports fourantennas (N=4) and includes a MIMO processor 120 z and two 2×2transceiver modules 710 a and 710 b. Each 2×2 transceiver module 710includes two transceivers for two antennas. Each transceiver includestransmit circuitry and receive circuitry for one antenna. Each 2×2transceiver module may be fabricated on a separate IC die, or multiple2×2 transceiver modules may be fabricated on the same IC die. MIMOprocessor 120 z couples to each transceiver module 710 via a respectiveset of baseband signals and control signals.

FIG. 8 shows a block diagram of an embodiment of 2×2 transceiver modules710 a and 710 b for MIMO unit 110 z. For this embodiment, transceivermodule 710 a includes two transceivers 810 a and 810 b, a voltagecontrolled oscillator (VCO) 820 a, a phase locked loop (PLL) 830 a, aninput buffer (Buf) 832 a, and an output driver (Driv) 834 a. Transceivermodule 710 b includes two transceivers 810 c and 810 d, a VCO 820 b, aPLL 830 b, an input buffer 832 b, and an output driver 834 b. Eachtransceiver 810 receives and processes a baseband input signal from MIMOprocessor 120 z and generates an RF modulated signal for one antenna150. Each transceiver 810 also receives and processes an RFE outputsignal from an associated remote front-end 140 (or an RF input signalfrom an associated antenna 150) and generates a baseband input signalfor MIMO processor 120 z.

When transceiver modules 710 a and 710 b are used to support fourantennas, transceiver module 710 a serves as the master module andtransceiver module 710 b is the slave module. VCO 820 a and PLL 830 awithin transceiver module 710 a are enabled and generate localoscillator (LO) signals used by all four transceivers 810 a through 810d for frequency upconversion and downconversion. VCO 820 b and PLL 830 bwithin transceiver module 710 b are disabled, driver 834 b and buffer832 a are also disabled, and driver 834 a and buffer 832 b are enabled.The LO signals from VCO 820 a are provided via driver 834 a and buffer832 b to transceivers 810 c and 810 d in the slave transceiver module710 b.

2×2 transceiver modules (as oppose to modules with more transceivers)may be efficiently used for multi-antenna stations with differentnumbers of antennas. For a multi-antenna station equipped with twoantennas, only one 2×2 transceiver module 710 is needed, and noadditional and unnecessary circuitry is wasted. In this case, VCO 820and PLL 830 are enabled to generate the LO signals for the twotransceivers 810 in the transceiver module, and driver 834 and buffer832 are disabled. For a multi-antenna station equipped with fourantennas such as the one shown in FIGS. 7 and 8, two 2×2 transceivermodules may be used for the four antennas, and only a small amount ofredundant circuitry is not used.

FIG. 9 shows a block diagram of an embodiment of transceivers 810 within2×2 transmitter modules 710. Each transceiver 810 includes a transmitterunit (TMTR) 960 and a receiver unit (RCVR) 980. The transmitter andreceiver units may be implemented with a super-heterodyne architectureor a direct-conversion architecture. For the super-heterodynearchitecture, frequency conversion between RF and baseband is performedin multiple stages, e.g., from RF to an intermediate frequency (IF) inone stage, and from IF to baseband in another stage. For thedirect-conversion architecture, frequency conversion is performed in asingle stage, e.g., from RF directly to baseband. For simplicity, FIG. 9shows an embodiment of transmitter unit 960 and receiver unit 980implemented with the direct-conversion architecture.

Within transmitter unit 960, a digital-to-analog converter (DAC) 962receives a stream of digital chips (which is the baseband input signal)from MIMO processor 120 z, converts the chips to analog, and provides ananalog baseband signal. A filter 964 then filters the analog basebandsignal to remove undesired images generated by the digital-to-analogconversion and provides a filtered baseband signal. An amplifier (Amp)966 amplifies and buffers the filtered baseband signal and provides anamplified baseband signal. A mixer 968 modulates a TX_LO signal from VCO820 a with the amplified baseband signal and provides an upconvertedsignal. A power amplifier 970 amplifies the upconverted signal andprovides an RF modulated signal, which is routed through a switch (SW)972 and provided to an associated remote front-end 140 for one antenna.

Within receiver unit 980, an LNA 982 receives an RFE output signal fromthe associated remote front-end 140 or an RF input signal from anassociated antenna 150 via switch 972. LNA 982 amplifies the received RFsignal and provides a conditioned signal having the desired signallevel. A mixer 984 demodulates the conditioned signal with an RX_LOsignal from VCO 820 a and provides a downconverted signal. A filter 986filters the downconverted signal to pass the desired signal componentsand to remove noise and undesired signals that may be generated by thefrequency downconversion process. An amplifier 988 amplifies and buffersthe filtered signal and provides an analog baseband signal. Ananalog-to-digital converter (ADC) 990 digitizes the analog basebandsignal and provides a stream of samples (which is the baseband outputsignal) to MIMO processor 120 z.

FIG. 9 shows an exemplary design for the transmitter and receiver units.For this design, the DAC and ADC are shown as being parts of thetransmitter unit and receiver unit, respectively. In general, thetransmitter and receiver units may each include one or more stages ofamplifier, filter, mixer, and so on, which may be arranged in a mannerdifferent from that shown in FIG. 9. The transmitter and receiver unitsmay or may not include the DAC and ADC, respectively.

FIG. 9 also shows an embodiment of MIMO processor 120 z, which includesvarious processing units that perform digital processing for datatransmission and reception. Within MIMO processor 120 z, a dataprocessor 914 performs encoding, interleaving, and symbol mapping fordata transmission and symbol demapping, deinterleaving, and decoding fordata reception. A spatial processor 916 performs transmitter spatialprocessing (e.g., for beamforming, spatial multiplexing, and so on) fordata transmission and receiver spatial processing (e.g., receiver matchfiltering) for data reception. A modulator 918 performs modulation,e.g., for orthogonal frequency division multiplexing (OFDM). Ademodulator 920 performs demodulation, e.g., for OFDM. Adetection/acquisition unit 922 performs processing to detect and acquiresignals from other transmitting stations. A main controller 930 controlsthe operation of various processing units within multi-antenna station100 and generates the various controls for transceivers 810 and remotefront-ends 140. For example, main controller 930 may generate the T/Rcontrol signal for remote front-ends 140. A power controller 932performs power management for multi-antenna station 100. For example,power controller 932 may determine whether or not to send DC power tothe remote front-ends. A random access memory (RAM) and a read onlymemory (ROM) 912 store data and program codes used by various processingunits within MIMO processor 120 z.

For clarity, the description above shows each remote front-end beingcoupled to one antenna, and each transceiver processing the RF signalsfor one antenna. In general, each remote front-end and/or eachtransceiver may be associated with a set of one or more antennas. If aremote front-end or transceiver is associated with multiple antennas,then these antennas may be viewed as a single (distributed) “antenna”for the remote front-end or transceiver.

The remote front-ends and transceiver modules described herein may beimplemented on RF integrated circuits (RFICs), with discrete components,and so on.

For example, each remote front-end may be implemented on one RFIC. Eachtransceiver module may be implemented on one RFIC, or multipletransceiver modules may be implemented on one RFIC, possibly along withother circuitry. The remote front-ends and transceiver modules may befabricated with various integrated circuit (IC) processes such ascomplementary metal oxide semiconductor (CMOS), bipolar, bipolar-CMOS(Bi-CMOS), gallium arsenide (GaAs), and so on. For example, each remotefront-end may be fabricated on one GaAs RFIC. Certain circuit components(e.g., inductors) may be printed on an IC die or implemented withMicro-Electro-Mechanical Systems (MEMS) technologies.

For simplicity, the control signals used to control the operation of theremote front-ends and the transceiver modules are shown as beinggenerated by MIMO processor 120 in the description above. In general,these control signals may be generated by various units such as, forexample, an application specific integrated circuit (ASIC), a digitalsignal processor (DSP), a digital signal processing devices (DSPD), aprogrammable logic device (PLD), a field programmable gate array (FPGA),a processor, a controller, a micro-controller, a microprocessor, or someother electronic unit designed to perform the functions describedherein.

The previous description of the disclosed embodiments is provided toenable any person skilled in the art to make or use the presentinvention. Various modifications to these embodiments will be readilyapparent to those skilled in the art, and the generic principles definedherein may be applied to other embodiments without departing from thespirit or scope of the invention. Thus, the present invention is notintended to be limited to the embodiments shown herein but is to beaccorded the widest scope consistent with the principles and novelfeatures disclosed herein.

1. An apparatus comprising: a first amplifier to receive and amplify afirst radio frequency (RF) signal and provide a first amplified RFsignal; a second amplifier to receive and amplify a second RF signal andprovide a second amplified RF signal; a first coupling unit to couplethe first RF signal from a first port to the first amplifier and tocouple the second amplified RF signal from the second amplifier to thefirst port; and a second coupling unit to couple the first amplified RFsignal from the first amplifier to a second port and to couple thesecond RF signal from the second,port to the second amplifier.
 2. Theapparatus of claim 1, wherein the first and second coupling units areswitches.
 3. The apparatus of claim 1, wherein the first and secondcoupling units couple the first RF signal from the first port to thefirst amplifier and couple the first amplified RF signal from the firstamplifier to the second port during a transmit portion, and furthercouple the second RF signal from the second port to the second amplifierand couple the second amplified RF signal from the second amplifier tothe first port during a receive portion.
 4. The apparatus of claim 1,wherein the first and second coupling units are duplexers.
 5. Theapparatus of claim 1, wherein the first amplifier is a power amplifier(PA).
 6. The apparatus of claim 1, wherein the second amplifier is a lownoise amplifier (LNA).
 7. The apparatus of claim 1, wherein the firstamplifier, the second amplifier, or both the first and second amplifiersare disabled when not used for communication.
 8. The apparatus of claim1, wherein the first amplifier is disabled during a receive portion, andwherein the second amplifier is disabled during a transmit portion. 9.The apparatus of claim 1, wherein the second port is coupled to one ofthe multiple antennas in the station.
 10. The apparatus of claim 1,wherein the first port is coupled to a transceiver in the station. 11.The apparatus of claim 1, wherein the first and second ports are coupledto different types of connectors.
 12. The apparatus of claim 1, whereinthe first and second ports are coupled to complementary types ofconnectors.
 13. The apparatus of claim 1, wherein the first and secondamplifiers and the first and second coupling units are fabricated on anRF integrated circuit (RFIC).
 14. The apparatus of claim 1, wherein thefirst and second amplifiers and the first and second coupling units arefabricated on a gallium arsenide (GaAs) integrated circuit (IC).
 15. Anapparatus comprising: means for amplifying a first radio frequency (RF)signal and generating a first amplified RF signal; means for amplifyinga second RF signal and generating a second amplified RF signal; meansfor coupling the first RF signal from a first port to the means foramplifying the first RF signal; means for coupling the first amplifiedRF signal to a second port; means for coupling the second RF signal fromthe second port to the means for amplifying the second RF signal; andmeans for coupling the second amplified RF signal to the first port. 16.The apparatus of claim 15, wherein the means for coupling the first RFsignal and the means for coupling the first amplified RF signal areactive during a transmit portion, and wherein the means for coupling thesecond RF signal and the means for coupling the second amplified RFsignal are active during a receive portion.
 17. The apparatus of claim15, further comprising: means for disabling the means for amplifying thefirst RF signal; and means for disabling the means for amplifying thesecond RF signal.
 18. A station equipped with a plurality of antennas,comprising: a plurality of transceivers, each transceiver performingsignal conditioning for radio frequency (RF) signals transmitted andreceived via an associated antenna; and a plurality of remotefront-ends, each remote front-end coupled to an associated transceiverand an associated antenna, each remote front-end amplifying a first RFsignal received from the associated transceiver to generate a firstamplified RF signal for transmission from the associated antenna andfurther amplifying a second RF signal received from the associatedantenna to generate a second amplified RF signal for transmission to theassociated transceiver.
 19. The station of claim 18, further comprising:a plurality of cables, each cable coupling one transceiver to theassociated remote front-end.
 20. The station of claim 19, wherein eachof the plurality of cables comprises a first cable to carry the first RFsignal and the second amplified RF signal between the transceiver andthe associated remote front-end.
 21. The station of claim 20, whereinthe first cable further carries DC power for the associated remotefront-end.
 22. The station of claim 20, wherein each of the plurality ofcables further comprises a second cable to carry at least one controlsignal for the associated remote front-end.
 23. The station of claim 22,wherein the first and second cables are bundled together.
 24. Thestation of claim 18, wherein the plurality of transceivers are arrangedin pairs, each pair of transceivers being implemented as a separatemodule.
 25. The station of claim 24, wherein the module for each pair oftransceivers comprises an oscillator to generate local oscillator (LO)signals for the transceivers in the pair.
 26. The station of claim 24,wherein multiple modules are implemented for multiple pairs oftransceivers, and wherein one module is designated to generate localoscillator (LO) signals for all transceivers in the multiple modules.27. A station equipped with a plurality of antennas, comprising: meansfor performing signal conditioning for radio frequency (RF) signalstransmitted and received via the plurality of antennas; means for poweramplifying RF modulated signals received from the means for performingsignal conditioning to generate amplified RF modulated signals fortransmission from the plurality of antennas; and means for low noiseamplifying RF input signals received from the plurality of antennas togenerate amplified RF input signals for transmission to the means forperforming signal conditioning, wherein the means for power amplifyingand the means for low noise amplifying are separate from the means forperforming signal conditioning.
 28. The apparatus of claim 27, furthercomprising: means for coupling the means for performing signalconditioning to the means for power amplifying and the means for lownoise amplifying.
 29. A transceiver module, comprising: first and secondtransceivers, each transceiver performing signal conditioning for radiofrequency (RF) signals transmitted and received via an associated set ofat least one antenna; an oscillator to generate local oscillator (LO)signals used by the first and second transceivers for frequencyconversion between baseband and RF; and a driver to receive the LOsignals from the oscillator and to drive the LO signals from thetransceiver module.
 30. The transceiver module of claim 29, furthercomprising: a buffer to receive external LO signals and to providebuffered LO signals used by the first and second transceivers forfrequency conversion between baseband and RF.
 31. The transceiver moduleof claim 30, wherein the oscillator is disabled if the buffer isreceiving the external LO signals.
 32. The transceiver module of claim29, further comprising: a phase locked loop (PLL) to control theoscillator to generate the LO signals at a predetermined frequency. 33.The transceiver module of claim 29 and fabricated on a single integratedcircuit (IC) die.
 34. A transceiver module, comprising: means forperforming signal conditioning for radio frequency (RF) signalstransmitted and received via at least two antennas; means for generatinglocal oscillator (LO) signals used for frequency conversion betweenbaseband and RF; and means for driving the LO signals from thetransceiver module.
 35. The transceiver module of claim 34, furthercomprising: means for buffering external LO signals and providingbuffered LO signals used for frequency conversion between baseband andRF.
 36. The transceiver module of claim 35, further comprising: meansfor disabling the means for generating the LO signals if the external LOsignals are received.